The present invention relates to liquid crystalline compounds and more particularly to novel crystalline compounds, which exhibit liquid crystallinity and, in addition, charge transport capability, and a process for producing the same.
Liquid crystalline compounds having various structures are known in the art and are widely used mainly as materials for information display devices using an electro-optic effect based on the alignment effect of liquid crystal molecules attained by application of voltage. Further, application of liquid crystalline compounds to optical shutters, optical stops, modulating devices, lenses, light beam deflection/optical switches, phase diffraction gratings, optical logic devices, memory devices and the like are under study. External simulation by heat, electric field, magnetic field, pressure or the like results in transition of the alignment of liquid crystal molecules which enables optical properties and electric capacity to be easily changed. Sensors and measuring instruments, utilizing this property, for temperature, electric field/voltage, infrared radiation, ultrasonic wave, flow rate/acceleration, gas or pressure have been studied in the art.
An object of the present invention is to provide liquid crystalline compounds having a novel structure and a process for producing the same.
The above object can be attained by the following present invention. Specifically, according to one aspect of the present invention, there is provided a liquid crystalline compound represented by the following general formula (I): 
wherein R1 and R2 each independently represent a straight-chain, branched or cyclic, saturated or unsaturated hydrocarbon group having 1 to 22 carbon atoms and may be attached directly to the aromatic ring without through X1 or X2; R3 represents a hydrogen atom, a cyano group, a nitro group, a fluorine atom, or a methyl group; and X1 and X2 each independently represent an oxygen atom, a sulfur atom, or a xe2x80x94COxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94Nxe2x95x90CHxe2x80x94, xe2x80x94CONHxe2x80x94, xe2x80x94NHxe2x80x94, xe2x80x94NHCOxe2x80x94, or xe2x80x94CH2xe2x80x94 group.
According to another aspect of the present invention, there is provided a liquid crystalline compound represented by the following general formula (II): 
wherein R1 and R2 each independently represent a straight-chain, branched or cyclic, saturated or unsaturated hydrocarbon group having 1 to 22 carbon atoms and may be attached directly to the aromatic ring without through X1 or X2; R3 represents a hydrogen atom, a cyano group, a nitro group, a fluorine atom, or a methyl group; X1 and X2 each independently represent an oxygen atom, a sulfur atom, or a xe2x80x94COxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94Nxe2x95x90CHxe2x80x94, xe2x80x94CONHxe2x80x94, xe2x80x94NHxe2x80x94, xe2x80x94NHCOxe2x80x94, or xe2x80x94CH2xe2x80x94 group; and Z represents a xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94Nxe2x95x90Nxe2x80x94, xe2x80x94CHxe2x95x90Nxe2x80x94, xe2x80x94CH2Sxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, or xe2x80x94Cxe2x89xa1Cxe2x80x94 group.
According to still another aspect of the present invention, there is provided a process for producing the liquid crystalline compound represented by the general formula (I), comprising the step of reacting a compound represented by the following general formula (1) with a compound represented by the following general formula (2): 
wherein R1, R2, R3, X1, and X2 are as defined above.
According to a further aspect of the present invention, there is provided a process for producing the liquid crystalline compound represented by the general formula (II), comprising the step of reacting a compound represented by the following general formula (3) with a compound represented by the following general formula (4): 
wherein R1, R2, R3, X1, and X2 are as defined above; and Y1 and Y2 are respectively groups which are reacted with each other to form a xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94Nxe2x95x90Nxe2x80x94, xe2x80x94CHxe2x95x90Nxe2x80x94, xe2x80x94CH2Sxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, or xe2x80x94Cxe2x89xa1Cxe2x80x94 group.
The present invention can provide novel liquid crystalline compounds having not only liquid crystallinity but also charge transport capability. The novel liquid crystalline compounds can be used in applications, where the conventional liquid crystalline compounds are used, and, in addition, are useful as materials for optical sensors, electroluminescence devices, photoconductors, space light modulating devices, thin film transistors, other sensors and the like, utilizing the charge transfer capability. In particular, some of the liquid crystalline compounds of the present invention have both electron transport capability and hole transport capability and, when mixed with a fluorescent material in order to use them as a material for an electroluminescence device, can provide luminescence.